<html>
<script>
  window.rafCount = 0;
  function animationCallback() {
    ++window.rafCount;
    console.log(`Animation frame callback #${window.rafCount}`);
    // Change document body background in a predictable manner.
    document.body.style.background = '#0000' + (window.rafCount * 10).toString(16);
    window.requestAnimationFrame(animationCallback);
  }

  function startRAF() {
    console.log('Requesting first animation frame');
    window.requestAnimationFrame(animationCallback);
  }

  function displayRAFCount() {
    console.log(`Animation frame count: ${window.rafCount}`);
  }
</script>
<body></body>
</html>
